The NIAID Repository for Biological Reagents and Reference Standards stores more than 2,000 different products ,including antisera against a wide variety of viruses and other infectious organisms, reference human and animal sera for a variety of infections, viral antigens, mycoplasmas, allergenic and immunologic reagents, and interferons. The NIAID is a designated World Health Organization (WHO) Collaborating Center for Antiviral Drugs and Interferon, and the Repository is responsible for distributing WHO interferon reference standards internationally. This facility also accepts and acquires new reagents deemed important to NIAID for distribution or for archiving. The availability of reference materials through this program activity provides an opportunity for individual investigators to test their working reagents against known reference standards. These reference reagents facilitate research funded by both government and private sector grants, including numerous projects of importance to NIAID.